The present invention relates to an emergency push-button having safe actuation, obtained through tripping, of the kind used for providing safety interventions on electrical, electromechanical or electronic devices or plants in order to obviate problems or to intervene the fastest possible in emergency situations.
Such a kind of emergency push-buttons are largely used for example, but not exclusively, on carrying or lifting devices, such as conveying belts, elevators, cranes, escalators and lifts, or in monitoring and alert plants against accidents, such as fires, blastings, floods, or crimes, such as stealings, hooliganisms, damages or the like.
There are already many emergency push-buttons and one of the objects sought to be obtained therethrough is a safe actuation, i.e. the safety that, once they are actuated, not only they interrupt their action or are deactuated, but they can be deactuated only at will by an explicit deactuating action. Further, said emergency push-buttons, must operate switches actuated by them even in case of failures of their components or damages to the contacts, such as light welding thereof.
All the emergency push-buttons, to meet the safety international regulations, are provided with a large knob or slider, having mushroom shape, which is actuable by a hand palm to permit the fastest and the safest the possible intervention.
One exemplary emergency push-button is described in U.S. Pat. No. 5,055,643 and which comprises a housing and a support rigidly connected to a movable actuation knob and axially movable therewith. The support acts on a releasing mechanism, operated by rotation of the knob about an axis parallel to the movement direction of the movable slider. The button further includes an axially movable member provided with at least one retaining tooth, which, upon lowering of the movable knob, rotates about an axis parallel to the moving direction of the knob, compelling the retaining tooth to release at least one protrusion provided on the housing and, once the movable member has cleared through a tripping action, it also rotates in a tripping manner carrying the retaining tooth to the position under the protrusion, preventing the movable member from moving back to a raised position thereof. The release of the retaining tooth may be obtained just through a rotating movement of the knob in a reversed direction with respect to the retaining movement. A cylinder lock may be provided within a knob.
It is now desired to provide an emergency push-button with a status indicator that is readily recognizable to a viewer.